Question: What is the Class IIIA combustible liquid with the lowest density whose instance of is occupational carcinogen?
Paraphrase: Name the  Class IIIA combustible liquid with the lowest density whose instance of is occupational carcinogen?
SPARQL (Wikidata): select ?ent where { ?ent wdt:P31 wd:Q21009058 . ?ent wdt:P2054 ?obj . ?ent wdt:P31 wd:Q21074597} ORDER BY ASC(?obj)LIMIT 5 
Answer: o-toluidine, aniline, formalin, phenylhydrazine, bis(2,3-epoxypropyl) ether